Light emitting diodes (LEDs) are considered as an ideal replacement for incandescent lamps for warning and guidance signaling applications owing to their high wall-plug efficiency and long lifetime. The LED based warning and guidance signaling apparatus disclosed in prior arts employ traditional T-pack LED units with luminous intensity less than a few tens of candelas. Thus they either are limited in visibility range or require a large number (several hundreds or even thousands) of LEDs to produce the desired luminous intensity. In addition, some mechanical rotating elements are generally used to produce a rotational emission effect, which elements lack in long-term reliability. Those previous disclosures include U.S. Pat. No. 5,608,290 issued to Hutchisson et al., U.S. Pat. No. 5,313,188 issued to Choi et al., and U.S. Pat. No. 6,753,762 issued to Jorba Gonzalez, and U.S. patent application Nos. 2002/0114161 disclosed by Barnett, and 2002/0145533 disclosed by Bushell et al.
Recent development in LED technology makes it possible to deliver high lumen power in one LED unit. Such LEDs have been used for maritime signaling applications as disclosed by Trenchard et al. in U.S. patent application No. 2004/0095777. These LED units have large emission area and beam divergence angle. Thus they can not be treated as point light sources. This makes it extremely difficult for LED beam profile control. In the Trenchard patent application, the signaling apparatus comprise twelve high flux LED units and the light beam produced by the entire LED array is controlled by a specially designed Fresnel lens. This lens is both complicated in structure and difficult to manufacture. In addition, such a lens design is not suitable to produce a rotational signaling effect since the divergence angle of the LED units can not be individually controlled.
Therefore, there is a need for an improved LED warning and guidance signaling apparatus with high luminous intensity and mechanical reliability, in which the apparatus is modular designed for efficient production, configuration, and installation, as well as for precise beam property control.